Conventional projectors have a number of difficulties and limitations. One of which is that all projection apparatus require sophisticated and complex optical engines and electronic components that are in-built into the apparatus. Frequently the complex and massive optical engines contain many optical components, such as illumination tubes, reflectors, integrators, lens set, and light pipes, etc., that are required to cooperate in a precise manner so as to enable the projection apparatus to work properly. However, the complexity of those conventional optical engines not only may cause assembly difficulty, but also it may be the cause of failing to achieve a compact and portable projector.
Another limitation of conventional projectors is that they are required to use color wheel and several polarizers, despite the use of foregoing components not only may reduce light utilization efficiency and color purity, but also may cause the projector to have more complicated optical pathway and thus indirectly increase the cost of assembly. Some efforts had been invested into developing projectors producing bright, high-quality, color images that are also compact and portable, such as those disclosed in U.S. Pat. Nos. 6,767,100 and 6,624,949. However, the color saturation of both of the two U.S. patented projecting apparatuses is still being limited by their using of traditional light sources and color wheel. Although it is possible to use light emitting diodes for replacing such traditional light sources and thus enhancing color purity, the use of polarizers for achieving required polarization is still unavoidable that may reduce light utilization efficiency. Therefore, as the conventional projection apparatuses require optical components, such as color wheel, light collimating lens, fly-eye lens array, and heat-dissipating fan, etc., they are usually built to be a massive device that are not portable.
Therefore, an alternative optical architecture is desired that substantially decreases the size and weight of the projection apparatus as compared with conventional projection apparatuses and significantly enhances color quality.